The present invention relates to a cellular network infrastructure for use in support of inbound roaming users and, more particularly, but not exclusively to the use of the CAMEL infrastructure, specifically intended for support of outbound roamers, to support inbound roamers.
The GSM CAMEL (Customized Applications for Mobile Network Enhanced Logic) standard is a standard for a cellular network infrastructure, which is aimed at providing services for outbound roamers. CAMEL works where both the home or HPMN (home public mobile network) and visited or VPMN (visited public mobile network) networks have installed CAMEL infrastructure, have a signed CAMEL roaming agreement between them, and have gone through the CAMEL integration process within their respective networks.
Upgrading network infrastructure to CAMEL involves the introduction or modification of several network components and is an intensive and expensive effort. One-by-one integration of the infrastructure and ongoing support for CAMEL roaming agreements provides an additional and significant cost for the operator. Currently, most of the roaming agreements between operators lack CAMEL capabilities, although CAMEL is gradually being introduced to more and more networks.
Another issue is that even if CAMEL is available, what it does is gives exclusive support to the home network to manage the roaming user and eliminates VPMN control almost totally from its inbound roaming subscriber once CAMEL has been activated. Thus, for example: if an inbound roamer for whom CAMEL services are available makes a dialing error, the only network that can play any part in fixing it is the HPMN, and in the vast majority of cases no fixing of the error in fact occurs. In many respects the VPMN has more ways to fix the dialing error since it knows of local numbering plans and the like.
CAMEL is a standard with an implementation which covers a core network and allows for support for outbound roamers specifically. Two CAMEL networks make an agreement between them and the result is integration of the networks, in the sense that outbound roamers on either of the networks who have come from the other network are provided with service support from their home network.
In all GSM networks, regardless of CAMEL support, the mobile telephones issue a location update trigger upon arriving at the VLR of the roaming network. Consequently, a user profile is sent from the home network to the roaming VLR. The operation to transfer the user profile in the roaming case is exactly the same as that which goes on in the national network when a user moves to another location. That is to say, triggers are used to transfer the user profile from the home location register HLR to the visitor location register VLR.
CAMEL, in addition, enables call control triggers, among other triggers, issued by the roaming network, to reach the home network not only during location update events. The CAMEL triggers allow the home network to take charge of the call and the home network is able to control the call with all the signaling necessary as if the roaming telephone is at the home network. Newer phases of CAMEL (such as phase 3) support not only call control, but SMS (short messaging service) and GPRS (general packet radio service) control. Triggers for MO (Mobile Originated) SMS and GPRS sessions initiated by roamers may be sent to the home network, which is be able to control the SMS/GPRS session (e.g. redirect, block if no credit, etc.). Using the present embodiments, the SMS and GPRS triggers can also be intercepted and dealt with by platform 14.
As mentioned above, putting the home network in charge can have disadvantages. For example there is the issue of knowing the local numbering plan and there are also well known national shortcodes, such as the numbers for the emergency services. A roamer from say the UK who is visiting the US would normally reach the US emergency services if he were to dial *911. However if Camel were in operation then his call to *911 in the US would go first to his UK operator who may not recognize the code at all, or at best would recognize after a delay and reroute the call.
There is thus a widely recognized need for, and it would be highly advantageous to have, a roaming system devoid of the above limitations.